const $ = db.command.aggregate

db.collection('mynote').doc('a6818b95-de6f-4355-9161-7cfbf1b67bbe')
  .update({
    data: {
      content: $.arraElemAt(['$content', 0]).remove()
    },
    success: res => {
      console.log("数据库操作结果成功", deleteData, res)
    },
    fail: err => {
      console.error("数据库操作结果失败", err)
    }
  })